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March 8, 2011 -- Five boys unable to urinate due to pelvic injury remain cured up to six years after getting new lab-grown urethras.

The successful report of "tissue engineered" urethras in patients comes from Wake Forest University researcher Anthony Atala, MD. In 2006, Atala's team reported the first successful implantation of lab-grown urinary bladders into humans.

All of the boys continue to do well, with normal or near-normal urinary flow. The boy most recently treated is now 15 years old and received his lab-grown urethra three years ago. The boy first treated is now 16 years old and received his lab-grown urethra over six years ago.

"Tissue-engineered urethras, repaired with patients' own cells, can be used to successfully treat complex urethral defects," Atala and colleagues report.

The urethras were grown on biodegradable mesh scaffolds made of a polyester compound. The scaffolds were seeded with cells taken from the boys' own bladders and incubated in the lab for four to seven weeks. They were then used to surgically repair damaged segments of the boys' urethras 1 1/2 inches to 2 1/2 inches in length.

While the team at Wake Forest Institute for Regenerative Medicine waited for six years to announce the successful use of lab-grown urethras, they have not been sitting still. Far more ambitious projects are in the works.

Because they are basically two-dimensional structures, it's a lot easier to create a urethra, bladder, or even blood vessels in the lab. It's a lot harder to create functional organs such as a kidney, which has some 20 different kinds of cells.

Atala and colleagues report their findings in the March 8 online edition of The Lancet.

SOURCES:Raya-Rivera, A. The Lancet, published online March 8, 2011.Sievert, K.-D. The Lancet, published online March 8, 2011.Atala, A. The Lancet, published online April 4, 2006.Chung, S.Y. The Lancet, published online April 4, 2006.